How to set up a legend with Graphview in Android Studio

Question

I have a screen on my app that display the following graph:

Is there a way to change my legend so that it can say what each color represents? Currently I can get the blue square to show up but it doesn't represent any of the numbers. Here is the code I'm using when creating the graph:

GraphView graph = (GraphView) findViewById(R.id.graph);

        BarGraphSeries<DataPoint> series = new BarGraphSeries<DataPoint>(new DataPoint[]{
                new DataPoint(1, personal),
                new DataPoint(2, fun),
                new DataPoint(3, work),
                new DataPoint(4, food),
                new DataPoint(5, commute),
                new DataPoint(6,bills)
        });


        graph.setTitle("Expenses");
        graph.addSeries(series);
        graph.getLegendRenderer().setVisible(true);
        graph.getLegendRenderer().setAlign(LegendRenderer.LegendAlign.TOP);
        series.setValueDependentColor(new ValueDependentColor<DataPoint>() {
            @Override
            public int get(DataPoint data) {
                return Color.rgb((int) data.getX() * 255 / 4, (int) Math.abs(data.getY() * 255 / 6), 100);
            }
        });
        series.setSpacing(50);

        series.setDrawValuesOnTop(true);
        series.setValuesOnTopColor(Color.RED);

        backToMainMenu();
    }

Answer 1

I don't think you need to customize the legend. The LegendRenderer class uses the title of each series of data to display what the bars on the chart represent.

series.setTitle("This will display in the legend.");

However, you only have one series of data in this example. If you must have labels in the legend for each bar, I suggest adding multiple series with different titles to your chart. Each series will have its own title and color.

// Each series represents one bar.
BarGraphSeries<DataPoint> series1 = new BarGraphSeries<DataPoint>(new DataPoint[]{ new DataPoint(1, personal)});
BarGraphSeries<DataPoint> series2 = new BarGraphSeries<DataPoint>(new DataPoint[]{ new DataPoint(2, fun)});
BarGraphSeries<DataPoint> series3 = new BarGraphSeries<DataPoint>(new DataPoint[]{ new DataPoint(3, work)});
BarGraphSeries<DataPoint> series4 = new BarGraphSeries<DataPoint>(new DataPoint[]{ new DataPoint(4, food)});
BarGraphSeries<DataPoint> series5 = new BarGraphSeries<DataPoint>(new DataPoint[]{ new DataPoint(5, commute)});
BarGraphSeries<DataPoint> series6 = new BarGraphSeries<DataPoint>(new DataPoint[]{ new DataPoint(6, bills)});

// Add titles to be displayed in the legend.
series1.setTitle("personal");
series2.setTitle("fun");
series3.setTitle("work");
series4.setTitle("food");
series5.setTitle("commute");
series6.setTitle("bills");

// Add color to your bars.
series1.setColor(Color.rbg(1,2,3));
series2.setColor(Color.rbg(4,5,6));
series3.setColor(Color.rbg(7,8,9));
series4.setColor(Color.rbg(0,1,2));
series5.setColor(Color.rbg(3,4,5));
series6.setColor(Color.rbg(6,7,8));

// Add each series to your graph.
graph.addSeries(series1);
graph.addSeries(series2);
graph.addSeries(series3);
graph.addSeries(series4);
graph.addSeries(series5);
graph.addSeries(series6);

// Display the legend.
graph.getLegendRenderer().setVisible(true);

Answer 2

you could use a custom legend renderer and extend the default implementation. https://github.com/jjoe64/GraphView/blob/master/src/main/java/com/jjoe64/graphview/LegendRenderer.java

Or you disable the legend in graphview, use a FrameLayout and overlay the graph with your very own views for your legend